Fifteen-year-old Hunter Gandee walked 57 miles over three days from his local elementary school in Lambertville, Mich., to Ann Arbor. But he didn’t do it alone – he had his eight-year-old brother Braden Gandee on his back.

For the second year in a row, the Gandee family completed their Cerebral Palsy Swagger – a walk intended to develop empathy and awareness of “the physical and mental challenges faced every day" by those, like Braden, who have been diagnosed with the disease and to encourage innovation in finding solutions to their needs. That the walk also became an unexpectedly large fundraiser, illustrating what makes a successful campaign at a time when many causes seek attention and donations.

Last year's walk was 40 miles long and took place over two days. This year, the Gandees’ trek was extended, giving them the chance to stop in more communities. When the pair crossed the finish line at the University of Michigan’s Pediatric Rehabilitation Center on Sunday, Hunter tweeted, "Beyond sore, beyond tired, beyond thankful, beyond blessed."

"It went great - we walked into a big crowd of people," Hunter told The Associated Press. "It was great to have everyone there. ... [Braden] was excited - not only that we were done finally, but everyone was there cheering him on."

Walking close to 60 miles, however, was not the only thing the Gandees accomplished. Although the walk was intended to raise awareness, not funds, more than $200,000 was donated toward building a handicap-accessible playground at Braden’s school over the course of the walk, Reuters reported. Now, the fundraising continues on a GoFundMe page, where as of Monday afternoon $595 had been sourced to support the playground, called the CP Swagger Shipyard.

MIT Sloan School of Management professor Catherine Tucker wrote in an op-ed for Yahoo Tech last year called “Why the Ice Bucket Challenge Proved Such a Runaway Success” that the campaign was successful because it was seen as new and authentic.

“The challenge was not something that a professional fundraiser came up with; rather, it was a grass-roots campaign. It felt genuine,” Sloan wrote. “This is important not just for its credibility but because the entire idea was so outlandish that it was unlikely to have originated in a typical marketing department, where it would have probably been rejected as a terrible idea that would never work.”

A high schooler carrying his little brother on his back generated that same sense of authenticity and originality. While charity walks are nothing new, this one had qualities that made it different: the length, for starters, and the fact that it was about one boy carrying his brother, not a crowd of donors walking together. But it did generate a crowd, as friends from school and families joined the walk.

Empathy is powerful, too, as Forbes contributor Rick Smith wrote in “The Science Behind the Success of the Ice Bucket Challenge.” “Selfless ideas evoke empathy, and empathy creates a direct physiological urge to act,” he wrote. “Watch someone perform a selfless act, and you are stirred to action.”

Perhaps adding to the authenticity was that the Gandees weren't overtly seeking donations. Others help channel and direct that effort. As Hunter said, the Gandees measured CP Swagger’s success not by the amount of money raised, but by the number of people reached compared with last year.

"We were able to reach more people," he told The Associated Press. "That's what our goal was."